1. Field of the Invention
The invention relates to a vehicle seat.
2. Description of Related Art
As shown in FIG. 8, a vehicle seat (hereinafter sometimes simply referred to as a “seat”) provided in a vehicle such as an automobile is constituted by a seat cushion 112 serving as a seat part for a seated person and a seat back 114 that receives the back of the seated person. The seat cushion 112 and the seat back 114 are normally connected to each other via a reclining mechanism 120, and the seat back 114 is tiltable in a front-rear direction (a left-right direction in the drawing). In the vehicle seat in FIG. 8, the reclining mechanism 120 is disposed via reclining plates 140.
The seat back 114 and the seat cushion 112 include a back frame 114F and a cushion frame 112F that form a frame of the vehicle seat, and each of the back frame 114F and the cushion frame 112F is formed into a frame shape. The back frame 114F and the cushion frame 112F include side frames 116 and 118 on the right and left sides thereof. Each of the side frames 116 of the back frame 114F and each of the side frames 118 of the cushion frame 112F are connected to each other via the reclining plate 140 described above. The reclining plate 140 is pivotably connected to the side frame 118 of the cushion frame 112F at two connection parts 142A and 142B using, for example, a bolt and a nut. The side frame 116 of the back frame 114F is tiltably and firmly connected to the reclining plate 140 using the reclining mechanism such as an engagement mechanism. The tilt operation with the reclining mechanism is performed about a shaft 138.
The vehicle seat is usually installed on the surface of a floor 122 such that the position in the front-rear direction is adjustable. Accordingly, the seat cushion 112 is disposed on the surface of the floor 122 via seat slide rail mechanisms 124. In each of the seat slide rail mechanisms 124, a lower rail 126 on the floor 122 side and an upper rail 125 on the seat cushion 112 side are slidably fitted to each other. In addition, the side frame 118 of the seat cushion 112 and the upper rail 125 are connected to each other using connection brackets 128 and 130 disposed in the front and the rear. With this, the seat is movable in the front-rear direction relative to the floor 122.
Note that the vehicle seat is provided with a seat belt device that holds the body of the seated person (occupant) from the viewpoint of safety of the occupant. Each of Japanese Patent Application Publication No. 7-108860 (JP 7-108860 A) and Japanese Patent Application Publication No. 2011-201327 (JP 2011-201327 A) describes a mounting structure of the seat belt device. A large load is applied to one end mounting part (belt anchor) of a seat belt 146 at the time of collision of a vehicle, and hence a seat belt anchor bracket 150 is mounted to the upper rail 125 of the seat slide rail mechanism 124 and the seat belt 146 is supported using the seat belt anchor bracket 150. With this, even in the case where the seat slides in the front-rear direction, it is possible to hold the occupant seated in the seat using the seat belt 146 appropriately. Note that the seat belt anchor bracket 150 is disposed in the rear of the seat cushion 112 such that the seat belt is properly attached to the seated person.
Incidentally, in the vehicle seat shown in FIG. 8, when an excessive load acts from behind as in the case where another vehicle collides with the vehicle from behind, an acting force for moving the seated person rearward relative to the seat is applied to the seated person. The rearward acting force applied to the seated person is received by the seat back 114, and is transmitted from the side frame 116 of the seat back 114 to the side frame 118 of the seat cushion 112 via the reclining plate 140. The seat cushion 112 is supported on the floor 122 via the front and rear connection brackets 128 and 130. The rearward acting force exerted on the entire seat starts to deform the seat such that the rear end portion of the seat cushion 112 sinks rearward and downward.
In order to restrict the sinking of the rear end portion of the seat cushion 112, portions (opposing portions) that come in contact with each other when the rear end portion of the side frame 118 is displaced downward are formed in the seat belt anchor bracket 150 and the side frame 118 of the seat cushion 112. In general, the opposing portions of the side frame 118 of the seat cushion 112 and the seat belt anchor bracket 150 are configured such that the entire opposing portions come in contact with each other at the same time.
In the above-described configuration shown in FIG. 8, the entire portions of the opposing portions of the side frame 118 of the seat cushion 112 and the seat belt anchor bracket 150 provided in the upper rail 125 of the seat slide rail mechanism 124 come in contact with each other substantially at the same time at the time of the collision from behind, and the load from the side frame 118 of the seat cushion 112 is received by the seat belt anchor bracket 150. Accordingly, a stress is concentrated on connection parts between the side frame 118 and the reclining plate 140, and there is a possibility that the bolts and the nuts in the connection parts are broken. Accordingly, it has been necessary to provide the connection part with a strength that allows the connection part to bear the stress concentration. Specifically, since the back frame 114F and the reclining plate 140 are firmly connected to each other using the reclining mechanism, the stress is concentrated on the two connection parts 142A and 142B between the reclining plate 140 and the cushion frame 112F. In particular, the seat back 114 tilts rearward at the time of the collision from behind, and hence the stress concentration occurs in the connection part 142B, and there has been a possibility that the bolt and the nut in the connection 142B is broken.